2$6 MOTION AND COORDINATION 



side, and the extensors of the fingers, on the back of the 

 forearm (Fig. 119). 



Of the hand: The adductor pollicis between the thumb 

 and the palm. 



Of % the trunk : The pectoralis major, between the upper 

 front part of the thorax and the shoulder ; the trapezius, 

 between the back of the shoulders and the spine ; the recttis 

 abdominiSj passing over the abdomen from above down- 

 ward ; and \hzerector spina, found in the small of the back. 



Of the hips: The glutens maximus, fastened between the 

 lower back part of the hips and the upper part of the femur. 



Of the upper part of the leg: The rectus femoris, the large 

 muscle on the front of the leg which connects at the lower 

 end with the kneepan. 



Of the lower leg: The tibia Us anticus on the front side, 

 exterior to the tibia, and the gastrocnemins, the large mus- 

 cle in the calf of the leg. This is the largest muscle of the 

 body, and is connected with the heel bone by the tendon 

 of Achilles (Fig. 1 19). 



The use of these muscles is, in most instances, easily 

 determined by observing the results of their contraction. 



HYGIENE OF THE MUSCLES 



The hygiene of the muscles is almost expressed by the 

 one word exercise. It is a matter of everyday knowledge 

 that the muscles are developed and strengthened by use, 

 and that they become weak, soft, and flabby by disuse. 

 The effects of exercise are, however, not limited to the 

 large muscles attached to the skeleton, but are apparent 

 also upon the involuntary muscles, whose work is so closely 

 related to the vital processes. While it is true that exer- 

 cise cannot be applied directly to the involuntary muscles, 

 it is also true that exercise of the voluntary muscles causes 



